1. Field of the Invention
The present invention is related to a circuit board, especially to a double-sided circuit board with a penetrating hole and a printed wiring board having the double-sided circuit board.
2. Discussion of the Background
From a viewpoint of enhancing electrical characteristics or the like, methods have been studied for filling with metal by plating inside a penetrating hole (through-hole) formed in a double-sided circuit board. For example, Japanese Laid-Open Patent Publication No. 2006-41463 describes that voids or the like are prevented from occurring by configuring a penetrating hole in a drum-like shape (hourglass shape).
The contents of Japanese Laid-Open Patent Publication No. 2006-41463 are incorporated herein by reference in their entirety in the present application.